3D Inspection of Mold Parts for Cavities, Cores and Inserts

A mold cavity is rarely a set of simple planes. It carries draft, radius blends, shutoff faces, water-line bosses and a parting line that has to seal under tonnage. Comparing the machined surface against the CAD model point by point shows where the steel actually sits, instead of inferring it from a handful of touch points.

We scan cavities, cores, slides, lifters, inserts and electrodes. The output is a color deviation map plus a report that ties each out-of-tolerance zone back to a feature the toolmaker can act on: a rib, a boss, a corner radius, a shutoff.

Mold parts are hard to measure because the surfaces that matter most are often the least accessible. A deep rib or a narrow slot may be invisible to a touch probe but easy for a structured-light scanner. The reverse is true for a polished shutoff face with a mirror finish.

Structured-light scanning captures millions of points in a single pass. It suits free-form surfaces, deep pockets and electrodes where you need overall shape, not just a few key dimensions. The limit is finish: a highly polished or mirror-like face scatters light and returns noisy data, so we dull the surface or switch methods.

Laser line scanning handles steeper walls than structured light and works well on textured or shot-blasted surfaces. It is slower per area but more forgiving on dark metals and tool steels where reflectivity changes across the part.

Contact CMM remains the reference for datums, hole positions, diameters and flatness. If the drawing calls out a Ø12 H7 bore or a flatness of 0.01 mm, the probe measures it directly. Scanning is excellent for shape; the CMM is excellent for size and location.

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  Structured lightBest for free-form cavities, cores and electrodes; needs a matte surface.
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  Laser scanningGood on steep walls, dark steel and shot-blasted or textured faces.
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  Contact CMMReference for datums, bores, diameters and flatness callouts.
• 4
  Optical / visionUseful for small inserts, fine features and edge-to-edge distances.

Two inspectors can scan the same mold insert and report different deviations. The difference is almost always the alignment. We lock the datum scheme to the drawing: primary plane, secondary axis, tertiary origin, in that order. If the drawing is ambiguous, we ask before scanning.

For a cavity insert, the parting plane is usually the primary datum and a leader pin bore sets the secondary. Aligning to the raw stock instead of the parting plane produces a deviation map that looks wrong everywhere and tells the toolmaker nothing useful.

We also note the machining setup. A part machined in one 5-axis setup keeps its datums consistent with the inspection alignment. A part moved between three setups may need a best-fit alignment per setup, and the report will say so.

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  Primary datumUsually the parting plane; establishes the main reference.
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  Secondary datumOften a leader pin bore or a locating edge.
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  Tertiary originSets the zero point for X and Y.
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  Best-fitUsed only when setup datums are not reliable.

A deviation map is a heat map. Red and blue mean the surface sits high or low relative to CAD; green means it is within tolerance. The map is only as good as the tolerance band you feed it. A cavity with a 0.05 mm band will look mostly green; the same cavity with a 0.01 mm band will light up.

We set the band from the drawing, not from a default. Critical shutoffs and sealing faces get the tight band. Non-critical ribs and clearance areas get a wider one. Mixing them into one map hides the features that matter.

For most mold parts we work to ±0.005 mm on critical dimensions, with an as-machined finish of Ra 1.6–3.2 μm and Ra 0.8–1.6 μm on functional faces. A fine Ra 0.2–0.8 μm polish is available when the surface has to release cleanly.

Inspection is not a final gate. We check raw material on arrival, monitor in-process dimensions on the machine, and run a full scan plus CMM check before shipment. If a feature drifts, the operator sees it while the part is still in the vise, not after it ships.

The report includes the deviation map, a CMM table for the callouts, the alignment scheme used, and the tolerance band. Photos of any flagged zone are attached. We can output in your format if you send a template.

Every part gets 100% inspection before it leaves the floor. Reports are available on request, and we can share them under NDA. Our historical late-delivery probability is below 2%.

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  Raw material checkGrade, hardness and certificate verified on arrival.
• 2
  In-process monitoringKey dimensions checked while the part is still on the machine.
• 3
  Final scan + CMMFull surface scan plus contact check on drawing callouts.
• 4
  Report packageDeviation map, CMM table, alignment scheme, tolerance band.

Scanning does not replace a CMM for size and location. If your drawing is dominated by hole positions, diameters and flatness, a contact report is faster and easier to defend. The scan adds shape information but does not improve those numbers.

A highly polished mold surface can be a poor scanning target. The reflection returns noisy points, and polishing the surface to make it scan means re-polishing it afterward. On a Class A shutoff, that is a risk we would rather avoid.

Very large parts have their own limit. Our maximum processing size is 4,000 mm, and large travel machines run 4,000 × 400 × 150 mm. A part near that envelope may need multiple scans stitched together, which adds alignment error at the seams.